The Muscle Tissue/Cell Culture/Diagnostics Core for this Wellstone Muscular Dystrophy Cooperative Research Center is a multifaceted laboratory that will be both a local and a national resource for muscular dystrophy research. There are two major goals of the Core. First, the Core will use approximately 4000 existing stored skeletal muscle biopsies to establish a muscle tissue repository. Among the existing muscle biopsies are more than 600 muscular dystrophy samples that include dystrophinopathies (Duchenne and Becker muscular dystrophy), limb-girdle muscular dystrophies, and congenital muscular dystrophies. We will accrue new specimens into the Core from a variety of sources: diagnostic muscle biopsies, therapeutic surgical procedures, endomyocardial biopsies, heart explants, skin biopsies, and autopsies. In addition to these tissues, we will establish fibroblast and myoblast cell lines from diagnostic muscle and skin biopsies. Patients with genetically defined muscular dystrophies will be recruited to undergo biopsies in order to maintain a widely representative spectrum of muscular dystrophy diagnoses. Well characterized tissues and cells from the Core will be made available to research investigators from other centers. The second goal of the Core is to establish a diagnostic resource. In this capacity it will provide diagnostic services that are not readily available through clinical laboratories, it will facilitate development of new diagnostic tests for transfer to the clinical laboratory, and will serve as a post-intervention biopsy evaluation resource for investigators conducting clinical trials. The Core will maintain patient confidentiality, and all testing will be quality controlled to meet CLIA licensing standards. Thus, the Muscle Tissue/Cell Culture/Diagnostics Core will establish a vital resource of muscular dystrophy tissues and cell cultures, provide a critical diagnostic link in expanding the number of patients with specific, molecular diagnoses, and serve as a national biopsy testing resource for clinical trials in muscular dystrophy patients.